The descendant is one of the main concepts in astrology. It is 1 of 4 main steps needed to prepare a natal chart. The natal chart or birth chart reflect the position of the stars at the hour and day of a person's birth.
The exact hour and day of birth are extremely important in calculating a precise natal chart, as well as the 4 axes of the horoscope. These are used to calculate the descendant, ascendant and MC/IC axes (Midheaven and Imum Coeli), as well as the arrangement of the planets in the different houses.
The ascendant is found in the First House of the natal chart. It is the zodiac sign that rose in the eastern horizon at the very moment of your birth.
Its opposite House, the Seventh House of the natal chart, is the descendant, meaning that calculating the descendant is directly linked to calculating the ascendant.
And while the ascendant defines who you are and what impression you'll make in others, the descendant defines your stereotypes and expectations, linked with everyone you communicate with.